Disk drives typically use heads residing on sliders to read from and write to the magnetic media. Read and write transducers residing in the head are flown at a small, controlled spacing above the magnetic medium during read and write operations. Thermal actuators, or heaters, may be used to control the spacing between the media and the read or write transducer. More specifically, heat generated by the heater causes local thermal expansion of the head. The thermal expansion results in protrusions of the head near the air-bearing surface (ABS). Protrusions in portions of the head near the ABS locally reduce the spacing between the head and magnetic media. The heater can be driven to induce sufficient heating for contact between the head and media. Such an operation is known as touchdown. This touchdown is intentional and is generally performed on each drive during initial drive calibration. The heater may also be used to otherwise control the spacing between the head and media.
Although heaters can be used to control the protrusion of the head, there may be drawbacks. A heater is typically included in the write transducer, but may not be in the read transducer of a head. Consequently, there are offsets between the protrusion of the write transducer and the protrusion of the read transducer. Portions of the read transducer may not have a sufficient protrusion to obtain the desired spacing between the read transducer and media (including touchdown). Further, even if the read transducer may protrude a sufficient amount, this may not be possible without inducing a protrusion in the write transducer that is larger than desired. Although multiple heaters may be included in a head, back end processing of the heat may be subject to significant variations. As a result, the heater in the read or write transducer may not be able to generate sufficient heat to provide the desired protrusion of the head.
Accordingly, what is needed is a system and method for providing improved touchdown detection.